Cisco 7942 Усунення несправностей та обслуговування - Сторінка 17

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Cisco 7942 Усунення несправностей та обслуговування

Troubleshooting and Maintenance

Table 1: Cisco Unified IP Phone Troubleshooting

Summary

Connecting a Cisco Unified IP Phone to another Cisco

Unified IP Phone

Poor quality when calling digital cell phones using

the G.729 protocol

Prolonged broadcast storms cause IP phones to reset,

or be unable to make or answer a call

Moving a network connection from the phone to a

workstation

Changing the telephone configuration

Phone resetting

General Troubleshooting Information

Explanation

Cisco does not support connecting an IP Phone to

another IP Phone through the PC port. Each IP Phone

should directly connect to a switch port. If phones are

connected together in a line using the PC port, the

phones will not work.

In Cisco Unified Communications Manager, you can

configure the network to use the G.729 protocol. The

default protocol is G.711. When using G.729, calls

between an IP Phone and a digital cellular phone will

have poor voice quality. Use G.729 only when

absolutely necessary.

A prolonged Layer 2 broadcast storm lasting several

minutes on the voice VLAN may cause IP Phones to

reset, lose an active call, or be unable to initiate or

answer a call. Phones may not come up until a

broadcast storm ends.

If you are powering your phone through the network

connection, you must be careful if you decide to

unplug the phone's network connection and plug the

cable into a desktop computer.

The network card in the computer cannot

Caution

receive power through the network

connection; if power comes through the

connection, the network card can be

destroyed. To protect a network card, wait

10 seconds or longer after unplugging the

cable from the phone before plugging it

into a computer. This delay gives the

switch enough time to recognize that there

is no longer a phone on the line and to stop

providing power to the cable.

By default, the network configuration options are

locked to prevent users from making changes that

could impact their network connectivity. You must

unlock the network configuration options before you

can configure them. See

Unlock and Lock Options

for details.

The phone resets when it loses contact with the Cisco

Unified Communications Manager software. This lost

connection can be due to any network connectivity

disruption, including cable breaks, switch outages,

and switch reboots.

Troubleshooting and Maintenance